1. Field of the Invention
The present invention relates to a stopper cylinder, which is capable of stopping a transported workpiece, and positioning the workpiece at a predetermined position, by means of a lock mechanism.
2. Description of the Related Art
A stopper cylinder has formerly been used, for example, so that a workpiece, which is transported by a conveyor line including, for example, a plurality of aligned roller conveyors, is stopped at a predetermined position. The stopper cylinder comprises a piston rod that is movable back and forth under an urging action, and a lever member, which engages the forward end of the piston rod. The lever member protrudes upwardly a predetermined length with respect to a transport surface of the conveyor line, from a gap formed between adjoining roller conveyors, such that the transport objective abuts against a guide roller that is provided on the lever member. Accordingly, the stopper cylinder functions as a stopper for stopping the transport objective.
In the stopper cylinder described above, in a locked state in which the lever member protrudes upwardly to stop the transport objective, the locked state is not released when the transport objective is transported in a direction opposite to the predetermined transport direction. Therefore, the operator cannot move the transport objective manually in a direction opposite to the preset transport direction.
As disclosed in Japanese Patent No. 3415425, the present applicant has suggested a stopper cylinder in which a locked state produced by the lever member can be released, even when the transport objective is transported in a direction opposite to the predetermined transport direction.
The stopper cylinder has a lock pin portion disposed at the end of the lever member. The lock pin portion engages with a bracket under a rotary action of the lever member. Accordingly, rotary movement of the lever member is regulated, so as to function as a stopper, and thereby halt transport of the transport objective. If the bracket is rotatable, the lock pin portion rotates the bracket while pressing the bracket, thus allowing the lever member to undergo rotary displacement when the transport objective abuts against the lever member and is pressed in a direction opposite to the predetermined transport direction. As a result, the lock pin portion disengages from the bracket, so as to release the regulated state of the lever member effected by the bracket. Accordingly, the transport objective can be transported in a direction opposite to the predetermined transport direction.